Yellow (hue / variety / modifier): Abbreviated (Y). A perceived colour hue resembling the average colour of the peel of a lemon (Citrus limon) or the petals of the dandelion flower (Taraxacum officinale). (See Figs. 9. 156 & 9. 152.) Yellow is one of the spectrum colours, positioned between green and orange, in the 560 nm to 590 nm wavelength region. Yellow is also spoken of as being a warm colour. In the diamond trade, yellow represents one of the twelve basic colour varieties. Yellow diamonds can also contain secondary colour modifiers such as greenish yellow (g-Y), brownish yellow (br-Y), orangish yellow (o-Y), olivish yellow (ol-Y), and grayish yellow (gy-Y). Yellow can also occur as a secondary colour modifier in other colour varieties such as yellowish brown (y-BR), yellow-orange (Y-0), etc. The range of colour tone for yellow diamonds is quite variable especially in saturation, e.g., pale (popcorn) yellow, dull (ochre) yellow, bright (lemon) yellow, and deep (amber) yellow. Lightness in yellow diamonds is limited to the very light through medium ranges; thus as lightness measures below the medium lightness level (L* < 55), yellow colours gradually appear brown or olive. Popular names for different mixtures of yellow are amber, banana, brass, buttercup, canary, chamois, champagne, chartreuse, citron, corn silk, cream, daffodil, dandelion, forsythia, gold, goldenrod, grapefruit, jonquil, lemon, manila, maple, marigold, mustard, ochre, oil, putty, saffron, straw, sulfur, sunflower, and wine